The present invention relates to a self-adjusting torque device.
During production process, some raw/auxiliary materials are fed and recovered in a winding form. In the course of feeding and recovering of a winding material, a torque of a driving motor M (M=R×F) is maintained constant. Since a radius R of the winding material varies with the feeding of the material, a tension F of the material is changed accordingly, which affects the accuracy of the feeding of material.
FIG. 1 is a diagram illustrating a tension variation during the course of feeding and recovering of a winding material in the related art. At an initial stage, the radius R1 of the winding material is the largest, while the tension F1 is the smallest; after an operation of a period of time, the radius R2 of the winding material is decreased, and the tension F2 is increased where the torque M is kept unvaried.
A known approach for solving the above problem is to provide three radius detecting sensors beside the material roll with each sensor corresponding to a respective predetermined radius. For example, a first sensor corresponds to a radius R1, a second sensor corresponds to a radius R2, and a third sensor corresponds to a radius R3. When the three sensors are triggered simultaneously, the motor outputs a torque M1=R1×F; when the second and the third sensors are triggered, the motor outputs a torque M2=R2×F; and when only the third sensor is triggered, the motor outputs a torque M3=R3×F. Thus, following the variation of the radius of the winding material (for example, R1, R2 and R3, respectively), the torque is varied accordingly (for example, M1, M2 and M3, respectively), so as to keep the tension F constant.
In the above approach, the variation of the torque suffers from abrupt changes; that is to say; the differences between the torques M1 and M2 and between M2 and M3 are very great, and thus a smooth and gradual change is not available. In addition, when the radius of the winding material is in a range between R1 and R2 or between R2 and R3, the tension F will continue to vary with the change of the radius and still results in inaccuracy of feeding and recovering of the winding material.